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United States Patent |
5,047,295
|
Dotzauer
,   et al.
|
September 10, 1991
|
Concrete roof tile
Abstract
A concrete roof tile is coated with an unfilled or aggregate- and/or
pigment-filled film of a copolymer containing (a) from 0.03 to 2% by
weight of tin in the form of a polymerizable organotin compound (b) from
0.5 to 5% by weight of (meth)acrylic acid, (meth)acrylamide and/or
vinylsulfonic acid and (c) from 0.1 to 5% by weight of carbonyl-containing
monomers crosslinked with certain dicarboxodihydrazides, besides (d) at
least two (meth)acrylic esters of C.sub.1 -C.sub.8 alkanols and/or styrene
as copolymerized units in such an amount and such mixing ratios that the
copolymer has a glass transition temperature of -15 to +10.degree. C.
prior to crosslinking.
Inventors:
|
Dotzauer; Bernhard (Maxdorf, DE);
Dersch; Rolf (Frankenthal, DE);
Vinke; Johannes (Neustadt, DE);
Hanciogullari; Harutyun (Birkenau, DE);
Schwartz; Manfred (Ludwigshafen, DE);
Berg; Volkmar (Graben, DE)
|
Assignee:
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BASF Aktiengesellschaft (Ludwigshafen, DE)
|
Appl. No.:
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461916 |
Filed:
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January 8, 1990 |
Foreign Application Priority Data
Current U.S. Class: |
428/500; 525/328.5; 525/329.4; 525/329.7; 525/330.2; 525/376; 526/240 |
Intern'l Class: |
B32B 027/00 |
Field of Search: |
428/500
526/240
525/328.5,329.4,329.7,330.2
|
References Cited
U.S. Patent Documents
3979354 | Sep., 1976 | Dyckman et al. | 526/240.
|
4064338 | Dec., 1977 | Russell | 526/240.
|
4098971 | Jul., 1978 | Phillip et al. | 526/240.
|
4121034 | Oct., 1978 | Beduarski et al. | 526/240.
|
4157999 | Jun., 1979 | Matsuda et al. | 428/541.
|
4191838 | Mar., 1980 | Merger et al. | 526/315.
|
4250070 | Feb., 1981 | Ley et al. | 525/376.
|
4267091 | May., 1981 | Geelhaar et al. | 526/316.
|
4485197 | Nov., 1984 | Yokoi et al. | 523/177.
|
4576838 | Mar., 1986 | Rosen et al. | 428/907.
|
4596724 | Jun., 1986 | Lane et al. | 428/907.
|
Primary Examiner: Lipman; Bernard
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier & Neustadt
Claims
We claim:
1. A concrete roof tile coated on at least one of its surfaces with an
unfilled- or aggregate- or pigment-filled film of a crosslinked copolymer
containing the following monomer units in copolymerized form:
(a) from 0.03 to 2% by weight of tin in the form of units of at least one
organotin compound having one or more polymerizable C.dbd.C bonds,
(b) from 0.5 to 5% by weight of units of at least one compound from the
group consisting of acrylic acid, methacrylic acid, acrylamide,
methacrylamide and/or vinylsulfonic acid,
(c) from 0.1 to 5% by weight of units of carbonyl-containing monomers
crosslinked with dihydrazides of aliphatic dicarboxylic acids of from 2 to
10 carbon atoms, and
(d) the difference to 100% by weight of units of at least two monomers
selected from the group consisting of the acrylic and methacrylic esters
of C.sub.1 -C.sub.8 -alkanols and styrene in such an amount and in such
mixing ratios that the copolymer has a glass transition temperature of
from -15.degree. to +10.degree. C. prior to crosslinking.
2. A concrete roof tile as claimed in claim 1, coated with a copolymer in
which the units of an organotin compound are those of tri-n-butyltin
methacrylate.
Description
The present invention relates to a coated concrete roof tile having
improved properties and to a process for producing same.
Concrete roof tiles are produced from mortars whose consistency permits the
final shaping The roof tile retains its shape even during the process of
hardening, which usually takes place at from 40.degree. to 100.degree. C.
Concrete roof tiles are prone to lime efflorescence; lime efflorescence is
produced by the reaction of calcium hydroxide on the surface of the roof
tile with the carbon dioxide in the air. Calcium hydroxide can get to the
surface of the roof tile not only during the process of hardening but also
under the conditions of weathering. The consequence is a stained,
unsightly roof. Concrete roof tiles, which usually have a pigment content,
are surface coated after shaping but prior to hardening, ie. when in the
"green" state, with coating compositions which are intended to prevent
lime efflorescence on the surface of roof covering materials, and then
stored for from 6 to 12 hours in hardening chambers, which are usually at
the abovementioned temperatures; in the course of this storage period they
become hard and the coating composition dries at the same time. On
occasion, after the tile has hardened, a further portion of coating
composition is applied to it and dried.
Coating compositions very widely used in the production of concrete roof
tiles are aqueous compositions formed from a binder dispersion, inorganic
aggregates such as chalk, quartz powder and iron oxide pigments, additives
for setting under the desired minimum film forming temperature (=MFFT),
for example sparingly volatile esters or hydrocarbons or plasticizers, and
also from pigment dispersers and antifoams. The pigment volume
concentration (PVC) of these coating compositions is about 40%.
The binders used are for example emulsion polymers based on n-butyl
acrylate or 2-ethylhexyl acrylate and styrene, the MFFT of the basic
polymer dispersion always being about 20.degree. C. and that of the
coating system about 5.degree.-8.degree. C.
These coatings have over the years been found to have the following
disadvantages:
The additives required for safe and complete film formation are only
incompletely removed in the course of the forced drying step and do not
guarantee an adequate calcium ion barrier from the start.
Nor does this phase always provide the similarly required barrier effect in
relation to water, so that premature erosion may occur in winter due to
the freezethaw cycle.
This represents a hazard for example for roofs made from concrete roof
tiles produced in the fall/winter period. The same is true of concrete
roof tiles which as usual were stored packed in the open, since it cannot
be ruled out that moisture can get into the packages as water of
condensation or as rain.
It is an object of the present invention to provide a coated concrete roof
tile which under all practically experienced storage and use conditions is
safe from lime efflorescence, has an improved barrier effect in relation
to water and shows improved protection against premature destruction by
temperature changes around freezing. A further object is to provide a
concrete roof tile which has the benefit of algicidal protection without
polluting the environment by the release of toxic substances. It is yet
another object of the present invention to provide a process for producing
such a concrete tile without the use of additives or auxiliaries which, in
the course of the disposal of wastes, might contaminate the wastewater or
groundwater.
We have found that these objects are achieved by a concrete roof tile
coated in a conventional manner on at least one of its surfaces with an
unfilled or aggregate- and/or pigment-filled film of a copolymer
containing the following monomer units in copolymerized form:
(a) from 0.03 to 2% by weight of tin in the form of units of at least one
organotin compound having one or more polymerizable C.dbd.C bonds,
(b) from 0.5 to 5% by weight of units of acrylic acid, methacrylic acid,
acrylamide, methacrylamide and/or vinylsulfonic acid,
(c) from 0.1 to 5% by weight of units of carbonylcontaining monomers
crosslinked with dihydrazides of aliphatic dicarboxylic acids of from 2 to
10 carbon atoms, and
(d) the difference to 100% by weight of units of at least two monomers
selected from the group consisting of the acrylic and methacrylic esters
of C.sub.1 -C.sub.8 -alkanols and styrene in such an amount and in such
mixing ratios that the copolymer has a glass transition temperature of
from -15.degree. to +10.degree. C. prior to crosslinking.
A concrete roof tile of this type is produced according to the present
invention by applying to at least one surface of the "green" roof tile an
aqueous coating composition containing
(A) a dispersed copolymer of
(A.sub.1) from 0.03 to 2% by weight (calculated as tin) of at least one
organotin compound having one or more polymerizable C.dbd.C bonds,
(A.sub.2) from 0.5 to 5% by weight of acrylic acid, methacrylic acid,
acrylamide, methacrylamide and/or vinylsulfonic acid,
(A.sub.3) from 0.1 to 5% by weight of at least one monomer having one or
more carbonyl groups and
(A.sub.4) the difference to 100% by weight of at least two monomers
selected from the group consisting of the acrylic and methacrylic esters
of C.sub.1 -C.sub.8 -alkanols and styrene in such an amount and such
mixing ratios that the copolymer has a glass transition temperature of
from -15.degree. to +10.degree. C.,
(B) from 0.2 to 3% by weight (based on dry copolymer) of at least one
water-soluble dihydrazide of an aliphatic dicarboxylic acid of from 2 to
10 carbon atoms,
(C) from 1 to 5% by weight (based on dry copolymer) of at least one
emulsifier selected from the group consisting of the fatty alcohol
sulfates and fatty alcohol ethoxylates, and
(D) up to 300% by weight (based on dry copolymer) of mineral aggregates
and/or color pigments, then, in the course of the high-temperature
hardening of the concrete roof tile, drying the composition to leave a
film and, optionally, after the high-temperature hardening, applying a
further layer of the composition and again drying it to leave a film.
The coating composition is advantageously prepared starting from an aqueous
dispersion of copolymer A having a viscosity at 23.degree. C. of from 0.5
to 2.5 Pa.s and preferably a pH of about 8.
The organotin compounds of the type mentioned under A.sub.1 are known or
obtainable by known methods Examples of such compounds are: tri-n-butyltin
acrylate, tri-n-butyltin methacrylate, tricyclohexyltin methacrylate,
tricyclohexyltin acrylate, triphenyltin acrylate, triphenyltin
methacrylate, tri-n-propyltin acrylate, tri-n-propyltin methacrylate,
triisopropyltin acrylate, triisopropyltin methacrylate, tri-sec-butyltin
acrylate, tri-sec-butyltin methacrylate, triethyltin acrylate, triethyltin
methacrylate, diethylbutyltin acrylate, diethylbutyltin methacrylate,
diethylamyltin acrylate, diethylamyltin methacrylate, diamylmethyltin
acrylate, diamylmethyltin methacrylate, propylbutylamyltin acrylate,
propylbutylamyltin methacrylate, diethylphenyltin acrylate,
diethylphenyltin methacrylate, ethyldiphenyltin acrylate, ethyldiphenyltin
methacrylate, n-octyldiphenyltin acrylate, n-octyldiphenyltin
methacrylate, diethylisooctyltin acrylate, diethylisooctyltin
methacrylate, di-n-butyltin diacrylate, di-n-butyltin dimethacrylate, the
tripropyltin monoester and diester of maleic acid, the tricyclohexyltin
monoester and diester of maleic acid, the triphenyltin monoester and
diester of maleic acid, the tri-n-butyltin monoester and diester of maleic
acid and the corresponding monoesters and diesters of itaconic and
citraconic acid, allyltri-n-butyltin, diallyldi-n-butyltin,
allyltricyclohexyltin, diallyldicyclohexyltin, allyltriphenyltin and
diallyldiphenyltin. Particularly effective organotin compounds are those
which contain an acryloyl or methacryloyl group and three alkyl groups of
from 3 to 6 carbon atoms bonded to the tin. Of these, tri-n-butyltin
methacrylate is preferred because it is readily available.
The organotin compounds are copolymerized into polymer A via their C.dbd.C
double bond(s) in such an amount that the tin content of the polymer is
from 0.03 to 2% by weight, preferably from 0.3 to 1% by weight.
Those of the monomers mentioned under A.sub.2 which carry carboxyl or sulfo
groups may be present in copolymer A in the form of the free acids or in
completely or partially neutralized form, in particular in alkali metal or
ammonium salt form.
Carbonyl-containing monomers A.sub.3 are monomers having at least one aldo
or keto group and at least one polymerizable double bond. Of particular
interest are acrolein, diacetone acrylamide, formylstyrene, vinyl alkyl
ketone, preferably of 4 to 7 carbon atoms, such as in particular vinyl
methyl ketone, vinyl ethyl ketone and vinyl isobutyl ketone, and/or
(meth)acryloyloxyalkylpropanals of the general formula
##STR1##
where R.sup.1 is --H or CH.sub.3, R.sup.2 is --H or C.sub.1 -C.sub.3
-alkyl, R.sup.3 is C.sub.1 -C.sub.3 alkyl, and R.sup.4 is C.sub.1 -C.sub.4
-alkyl. Such (meth)acryloyloxyalkylalkylpropanols can be prepared by the
process of German Patent Application P 27 22 097.9 by esterifying
.beta.-hydroxyalkylpropanals of the general formula
##STR2##
where R.sup.2, R.sup.3 and R.sup.4 are each as defined above, in the
presence of inert diluents and small amounts of sulfonic and mineral acids
at from 40.degree. to 120.degree., in particular at from 50.degree. to
90.degree.. Keto-containing monomers further include diacetone acrylate,
acetonyl acrylate, diacetone methacrylate, 2-hydroxypropyl acrylate
acetoacetate, 1,4-butanediol acrylate acetoacetate and 2-ketobutyl
(meth)acrylate. The amount of carbonyl or keto-containing copolymerized
comonomer is preferably from 1 to 4% by weight, based on copolymer A.
The monomers of the group mentioned under A.sub.4 supply by weight by far
the largest proportion of copolymer A. Their identity and mixing ratios
therefore chiefly dictate the level of the glass transition temperature of
copolymer A. The general principles which apply here are known to the
person skilled in the art. They shall therefore only be sketched out here
in condensed form: A distinction is made between hardening and softening
monomers. The terms hardening and softening refer to monomers which in the
literature are occasionally imprecisely chararacterized as hard and soft
respectively, ie. monomers which, polymerized on their own, produce hard
or soft homopolymers. A hardening monomer, then, is a monomer whose
homopolymer has a glass transition temperature of from about 25.degree. to
120.degree. C., while a softening monomer is a monomer whose homopolymer
has a glass transition temperature of from about -60.degree. to
+25.degree. C. It is true that the boundary between these two groups of
monomers is fluid, but typical representatives are known for both groups.
Typical hardening monomers are for example styrene, methyl methacrylate and
tert-butyl acrylate. Of these, methyl methacrylate and styrene are
preferred for the purposes of the present invention.
Typical softening monomers are for example acrylic and methacrylic esters
of non-tertiary alkanols of from 2 to 8 carbon atoms. Of these, n-butyl
acrylate, n-butyl methacrylate and ethylhexyl acrylate are preferred for
the purposes of the present invention.
The person skilled in the art knows that copolymers which contain both
softening and hardening monomers as copolymerized units have glass
transition temperatures between those of the respective homopolymers. It
is therefore a simple matter to set predetermined glass transition
temperatures by selecting the monomers and their mixing ratios. Typical
combinations of monomers of the type mentioned under A.sub.4 whose glass
transition temperatures are within the range to be obtained according to
the invention are for example (in % by weight):
65% of 2-ethylhexyl acrylate, 35% of styrene,
55% of 2-ethylhexyl acrylate, 45% of styrene,
60% of 2-ethylhexyl acrylate, 20% of methyl methacrylate, 20% of styrene,
55% of 2-ethylhexyl acrylate, 35% of butyl methacrylate, 10% of styrene,
25% of butyl acrylate, 25% of 2-ethylhexyl acrylate, 50% of styrene,
60% of butyl acrylate, 40% of styrene,
30% of butyl acrylate, 30% of 2-ethylhexylacrylate, 20% of styrene, 20% of
methyl methacrylate,
35% of butyl acrylate, 30% of methyl methacrylate, 35% of butyl
methacrylate
The additional incorporation of the monomers mentioned under A.sub.1 to
A.sub.3 likewise affects the glass transition temperatures of copolymers
A. For this reason it may be necessary to adapt the above-indicated mixing
ratios of monomers A.sub.4.
The glass transition temperature can be determined by conventional methods,
for example from the measurement of the modulus of elasticity in a creep
test as a function of the temperature or by using differential thermal
analysis (DTA) (see on this matter A. Zosel, Farbe and Lack 82 (1976),
125-134).
The aqueous dispersons of copolymer A may be prepared in a conventional
manner by copolymerizing monomers A.sub.1 to A.sub.4 in aqueous emulsion
using customary emulsifiers and dispersants, and usually have a copolymer
A concentration of from 40 to 60% by weight. The emulsifying and
dispersing component usually comprises from 0.2 to 3% by weight, based on
the amount of copolymer A, of anionic and/or nonionic emulsifiers, such as
sodium dialkylsulfosuccinate, sodium salts of sulfated oils, sodium salts
of alkanesulfonic acids, sodium alkylsulfate, potassium alkylsulfate,
ammonium alkylsulfate, alkali metal salts of sulfonic acids, alkoxylated
C.sub.12 -C.sub.24 -fatty alcohols and alkoxylated alkylphenols, and also
ethoxylated fatty acids, fatty alcohols and/or fatty amides, ethoxylated
alkylphenols, or sodium salts of fatty acids, such as sodium stearate and
sodium oleate. The preferred emulsifiers are fatty alcohol sulfates and
fatty alcohol ethoxylates, since they are particularly readily
biodegradable. The resulting fine dispersions are particularly highly
suitable for the present invention. The average particle size of the
dispersions according to the present invention is usually clearly below
100 nm. A typical weight distribution, determined using an analytical
ultracentrifuge (W. Maechtle, Makromolekulare Chemie
______________________________________
185 (1984), 1025), is
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D.sub.10 60 nm,
D.sub.50 65 nm,
D.sub.90 70 nm.
______________________________________
The dispersion of copolymer A has added to it component (B), viz. at least
one water-soluble dihydrazide of an aliphatic dicarboxylic acid containing
from 2 to 10, preferably from 4 to 6, carbon atoms, advantageously in an
amount of from 0.05 to 1, preferably from 0.4 to 0.6, mole per mole of
carbonyl groups present in copolymer A. Specific examples of components
(B) are: oxalodihydrazide, malonodihydrazide, succinodihydrazide,
glutarodihydrazide, adipodihydrazide, sebacodihydrazide, maleodihydrazide,
fumarodihydrazide and itaconodihydrazide.
The dispersion of components (A) and (B) is capable of forming, at room
temperature, a bright, clear and tough/flexible film of low water uptake;
after storage in water for 24 hours, the water content is less than 10%,
usually less than 5%. The film is free of plasticizers and film forming
agents.
The dispersion tends to produce little foam, if any, but for use in coating
compositions it can be advantageous to add antifoam. Highly suitable
antifoams are for example silicone-based products.
The abovementioned organotin compounds are completely incorporated into the
polymer chains and they are also very stable to hydrolysis. For instance,
the serum of the copolymer A dispersions is found to have a tin
concentration of about 1 ppm irrespective of whether 0.1 or 5% of
organotin compound was used.
Having an LC.sub.50 (96 h, Salmo gairdneri RICH.) of above 1,000 mg/l,
these polymer dispersions have no acute toxicity for fish.
Dispersions of copolymers A must accordingly be considered more favorable
than those which contain sparingly soluble zinc dithiocarbamate and/or
benzimidazole derivatives as state of the art biocides. The latter have
LC.sub.50 values (golden orfe) of below 500 mg/l.
Surprisingly, the very low concentration of the highly hydrolysis-resistant
copolymerized tin component is sufficient to prevent the growth of algae,
such as Chlorella vulgaris.
For conversion into coating compositions, the dispersions of copolymers A
containing components (B) are admixed in a conventional manner with
inorganic fillers and color pigments and brought to the desired viscosity
with water. Suitable inorganic fillers are for example: chalk, quartz
powder and/or baryte. Examples of color pigments are iron oxide red and
black pigments
Such a coating composition has in principle the following makeup:
40% of polymer dispersion with or without additional emulsifier as per (C)
20% of chalk
15% of quartz powder
5% of iron oxide pigment
about 20% of water.
The pigment volume concentration of this formulation is about 45%, and its
viscosity at 150 mPa.s (82 s.sup.-1), measured by German standard
specification DIN 53 018.
The concrete roof tile is produced in a conventional manner from
ready-mixed concrete by an extrusion process. In the course of this
process, it already receives its final shape. The coating composition is
applied in a conventional manner, preferably by spraying, to the "green
roof tile", ie. to the still wet concrete The total addon is about 300
g/m.sup.2 (dry). The coated roof tile is introduced into a chamber. There,
the concrete sets at from 40.degree. to 65.degree. C. in the course of
from 6 to 12 hours, and the copolymer of the coating composition forms a
film.
Thereafter the roof tile is preferably sprayed a second time with the
coating composition. Drying takes place in a tunnel furnace at around
100.degree. C. ambient air temperature. The tunnel furnace and the
subsequent cooling line are designed in such a way that complete film
formation takes place.
The very uniform coatings have an outstanding barrier effect against
calcium ions. They do not show any lime efflorescence following a
waterbath treatment A particularly surprising feature is the long lifetime
of the coatings as determined in a freeze-thaw cycle test, an accelerated
weathering test in line with German standard specification DIN 52 104
customary in the concrete roof tile industry. The roof tiles according to
the present invention survive at least twice as many, namely at least
1,200, freeze-thaw cycles without damage as those of the prior art, where
damage is likely after from 300 to 600 freeze-thaw cycles.
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